The types of household water purifiers that are connected directly to the faucet (tap) of a water pipe and purify tap water with a filter material have widely been used. The filter material generates purified water by catching impurities contained in the tap water, such as inorganic particles and bacteria.
Various water purifiers have conventionally been proposed. In Patent Document 1 the inventor of the present application discloses a water purifier capable of cleansing (backwashing) a filter material by causing tap water to flow in the opposite direction. In the following description, purifying tap water with a filter is referred to as “water purification mode,” and cleansing (backwashing) the filter material by causing water to flow in the direction opposite to the direction of the water in the water purification mode is referred to as “backwashing mode.”
FIG. 19 shows a water purifier 101 that has the same basic configuration as the one described in Patent Document 1. This water purifier 101 has an attachment main body 110 that is attached to a faucet F of a water pipe, and a water purification main body 120 mounted onto the attachment main body 110 so as to be rotatable relative to the attachment main body 110 and capable of purifying tap water flowing from the water pipe by means of a filter material. The attachment main body 110 is provided with an inlet 111 having the faucet F connected to the upper side thereof and having the tap water flowing thereto, a purified water outlet 112 out of which the purified water flows, a drainage water outlet (not shown) out of which drainage water obtained as a result of backwashing flows, a tap water outlet 114 out of which the tap water flows as is, an inflow passage P111 that communicates with the inlet 111, a purified water outflow passage P112 that communicates with the purified water outlet 112, a drainage water outflow passage (not shown) that communicates with the drainage water outlet, and a tap water outflow passage P114 that communicates with the tap water outlet 114. The water purification main body 120 consists of a water purification portion 120A provided with a partition wall member 127 stacked with a first filter material 125 (and a backwashing second filter material 126), a valve portion 1208 inserted and rotatably mounted into a valve-portion insertion-hole 115 of the attachment main body 110, and is provided with a first flow passage P121, a second flow passage P122, a third flow passage P123, and a fourth flow passage P124.
This water purifier 101 switches among the water purification mode, the backwashing mode and the tap water mode by rotating the water purification main body 120 with respect to the attachment main body 110 to change the passages through which the water flows. In the water purification mode (in the state shown in FIG. 19), the inflow passage P111 of the attachment main body 110 communicates with the first flow passage P121 of the water purification main body 120 to enable purification of the tap water using the first filter material 125, and the resultant purified water flows out of the purified water outlet 112 through the second flow passage P122 and the purified water outflow passage P112. In the backwashing mode, the inflow passage P111 of the attachment main body 110 communicates with the third flow passage P123 of the water purification main body 120 to enable purification of the tap water using the second filter material 126, and the resultant purified water passes through the first filter material 125 to backwash the first filter material 125, and passes through the first flow passage P121 and the drainage water outflow passage (not shown) communicating therewith, to cause the drainage water to flow out of the drainage water outlet (not shown). In the tap water mode, the inflow passage P111 of the attachment main body 110 communicates with the tap water outflow passage P114 of the attachment main body 110 via the fourth flow passage P124 of the water purification main body 120, to cause the tap water to flow out of the tap water outlet 114.